Preheat the oven to 325F and line a baking sheet with parchment paper.
In a large bowl, whisk together the almond flour, sweetener, baking powder, and salt. Stir in the avocado oil, egg, and maple extract until the dough comes together. Then stir in walnut baking pieces.
Turn the dough out onto the prepared baking sheet and form into a low, flat log, about 10 x 4 inches. Bake 25 minutes, or until lightly browned and firm to the touch. Remove from the oven and let cool 30 minutes. Reduce the oven temperature to 250F.
With a large sharp knife, gently slice the log into 15 even slices (try to cut straight down rather than sawing back and forth).
Separate the slices and spread them around the baking sheet. Bake another 30 minutes, then turn off the oven and let stay inside until cool. Keep your eye on them in case they brown too quickly.
For the glaze, whisk together the sweetener with the water and maple extract. Drizzle over the cooled biscotti and let set 30 minutes.